/ ˈkɑːsl; NAmE ˈkæsl/ noun
1.
a large strong building with thick high walls and towers, built in the past by kings or queens, or other important people, to defend themselves against attack
—see also sandcastle
2.
(also rook ) ( in chess ) any of the four pieces placed in the corner squares of the board at the start of the game, usually made to look like a castle
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IDIOMS
- (build) castles in the air
—more at Englishman
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WORD ORIGIN
late Old English : from Anglo-Norman French and Old Northern French castel , from Latin castellum , diminutive of castrum fort.